1. Field of the Invention
This invention relates generally to air cleaning systems of the pulse-jet cleaned filter type, which include provision for cleaning of the filter media by periodically generating a reverse pulse of air through the filter media. More specifically, the invention relates to a support member for a plurality of pleated media filter cartridges, which includes a "venturi" outlet for each cartridge, at which the reverse pulse of compressed air is directed, which is located within the dirty air chamber of the filter system and does not extend into the clean air plenum of the system.
2. Description of the Prior Art
Many prior art industrial filter houses use the pulse-jet cleaning principle, which comprises the step of directing a volume of compressed air, released rapidly through a diaphragm valve and nozzle, at the venturi mounted in the filter element outlet. The sudden pulse of air pressurizes the filter element in the reverse air flow direction, and blows off dust accumulated in the element. Dust so loosened drops into a hopper from which it may be extracted.
Pulse-jet type filter houses normally comprise two working chambers. The first of these is the dirty air chamber, in which the filtering media is located. The most commonly used filter elements for this application are either mesh bag-type elements, or, pleated media cartridges, similar to the familiar pleated paper automotive air filter. The second working chamber is the clean air plenum, which is in fluid communication with a flow inducing means on its down stream end, and the "clean side" of the filter elements on its upstream end. The flow inducing means create a vacuum situation within the clean air plenum, which negative pressure is distributed evenly to each filter element outlet by the plenum. This plenum also typically contains all the plumbing required for pulse jet cleaning of each element.
This plumbing includes a venturi mounted in the outlet of each element, a nozzle directed at each venturi, and some sort of manifold in fluid communication with each nozzle at a source of compressed air. This typical arrangement for bag houses is illustrated by patents to Carr, U.S. Pat. No. 3,594,922, and to Reinaur, U.S. Pat. No. 3,630,005. The typical arrangement where pleated media filter cartridges are used is shown in Torit Donaldson TD2300 and TD6120 filter houses.
A third, passive, chamber included in most filter houses is the hopper, the size of which is determined by the repose angle of the dusts, and the plan area of the filter house.
It is often of concern that a filter house for a particular application occupy as little plant space as possible, while still providing sufficient air cleaning capacity. It has been found that, generally speaking, pleated media cartridges can offer the same amount of filter media area as bag filters, while occupying much less volume. Consequently, the working volume of the dirty air chamber in filter house utilizing cartridges, and, consequently, the overall working volume of such filter houses, can be cut down, while still maintaining flow capacity. This is reflected in the fact that bag houses have an average air flow of about thirty cubic feet per minute per unit of working volume, whereas cartridge-type houses achieve an average air flow of sixty CFM per unit of working volume. "Working volume" is defined as the sum of the volumes of the dirty air chamber and the clean air plenum.
Until the present invention, nothing has been done to further decrease working volumes by decreasing the size of the clean air plenum. This size has been dictated by the considerations of evenly distributing air flow from the flow inducing source to the filter element outlets, and of providing sufficient space to house the reverse pulse plumbing, and also of providing enough room for service access. One of the major space considerations was the length of the venturies mounted in the element outlet.
In general, the prior art has not shown, or taught, how to achieve a ratio of dirty air chamber volume to clean air plenum volume of better than 1:1. This means that, in determining the amount of plant space, or mine space which a filter house will occupy (disregarding hopper space), one would determine the amount of filter media required for the job, i.e., the number of cartridges it would take to clean the required airflow, determine the volume that these cartridges would occupy, and double that volume.
In such applications as coal mining, where a high airflow is required, even the best of the current cartridge-type filter houses occupy too much working space in the mine.